This invention relates generally to ball-point pens for writing with aqueous or water-soluble inks. More particularly, the invention relates to improvements in a ball-point pen for water-soluble inks of a simple and inexpensive construction by which, within the barrel of the pen, evaporation and leakage of ink from an ink reservoir and/or an ink feed core are prevented.
The type of ball-point pen with which this invention is concerned uses a water-base or water-soluble ink of high volatility and excellent fluidity. It has been customary, in a ball-point pen of this type, to provide some kind of shielding means between a vent hole and an ink reservoir or an ink feed core for conducting ink therefrom to a ball socket part for reasons arising from the position of the vent hole.
More specifically, many of the ball-point pens for water-soluble inks of this character have been of the cap type in order to assure airtightness within the pen barrel when the pen is not in the state of writing. Accordingly, the vent hole, which communicates with the ink reservoir is ordinarily formed through the wall of the barrel at its front end part. Furthermore, since the front end part of the ink reservoir, in which an ink feed core is imbedded, is exposed, leakage of the ink within the ink reservoir into the interior of the barrel is caused by an unbalanced state occurring between the pressure within the ink reservoir and outside pressure as a result of temperature variation or by some impact applied to the pen when it is assuming an orientation with its ball point holder pointed downward. Eventually, this ink which has thus leaked further leaks out of the barrel through the vent hole.
Various measures and structural means for preventing this result have been proposed. However, these proposals have entailed complicated or high-cost solutions. Furthermore, difficulties have been encountered in the practical application of these proposals to automatic assembly processes for the production of writing instruments of this character. These processes have recently been attracting much attention among the manufacturers.
The use of effective automatic assembly processes for the production of writing instruments of this character requires simplicity in the construction of the instruments. This is generally incompatible with expedience and reliability in practical use of the writing instruments. When consideration is given to adaptability to effective automatic assembly processes, expedience and reliability are sacrificed, while if consideration is given to expedience and reliability, adaptability to automatic assembly processes is impaired. These results are due to the complicated construction of the writing instruments.